Page:Scientific results HMS Challenger vol 18 part 2.djvu/761

Rh

Definition.— with polygonal meshes in the network, the tubes of which are connected in different directions and form the spongy wall of a spherical shell. No radial tubes prominent over the surface.

The genus Aulodictyum differs from Aulonia, its ancestral form, in the development of a spongy framework in the thickened wall of the spherical lattice-shell. It bears therefore to the latter the same relation as Auloplegma does to Aularia. But the outer surface of the hollow sphere is in Aulodictyum completely smooth, as well as the inner, and bears no radial tubes. Only one species of this genus has been observed.

1. Aulodictyum hydrodictyum, n. sp.

Shell spherical, smooth on the outer and inner surfaces, composed of an irregular framework of straight and smooth cylindrical tubes; its meshes very irregular, of unequal size and various forms. The diameter of the sphere is about six or eight times as great as the thickness of its reticular wall.

Dimensions.—Diameter of the sphere 2 to 3, of its meshes 0.1 to 0.2; breadth of the bars 0.01.

Habitat.—Antarctic Ocean, Station 157, depth 1950 fathoms.

Cannosphærida, Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 6.

Definition.— with two concentric spherical or subspherical shells, which are connected by numerous thin, tubular, radial beams. Inner shell simple, spherical or ovate, solid or latticed, with a peculiar mouth. Outer shell spherical or polyhedral, articulate, composed of hollow tangential tubes, which are separated by astral septa at the stellate nodal points. From the latter arise hollow radial tubes, whilst the inner radial beams, connecting the two shells, are inserted in the middle of the tangential tubes. No peculiar mouth in the outer shell. Central capsule enclosed by the inner shell.

The family comprises a small number of remarkable  which are rare and found only in a few localities. They differ from all the other in the possession of two concentric spherical shells, which are connected by radial beams, and the inner of which is quite simple, like that of the Medusettida,